Counterbalance system for a marine loading arm



July 15, 1969 P. J. BlLY 3,455,333

COUNTERBALANCE SYSTEM FOR A MARINE LOADING ARM Filed Jan. 17, 1967 4Sheets-Sheet 1 INVENTOR PETER J. BILY M [U W ATTORNEY July 15, 1969 P JB|| Y 3,455,333

COUNTERBALANCE SYSTEM FOR A MARINE LOADING ARM Filed Jan. 17, 1967 4Sheets-Sheet 2 N v Q #1 g i 00 8. Q R N 3 Ln Q Q m J- T IF'II3 EIINVENTOR. PETER J. BILY Z Q/ W ATTORNEY FIG--QA July 15, 1969 BILY3,455,333

COUNTERBALANCE SYSTEM FOR A MARINE LOADING ARM Filed Jan. 17. 1967 4Sheets-Sheet I5 LO WEE/N6 6 8 RAISING 68 ATTORNEY July P B| YCOUNTERBALANCE SYSTEM FOR A MARINE LOADING ARM Filed Jan. 17, 1967 4Sheets-Sheet 4 "F" IB q[:

ENS/f5 J U l 94 86 9 i lfi BYMMW ATTORNEY United States Patent US. Cl.137615 6 Claims ABSTRACT OF THE DISCLOSURE A marine loading arm havingan adjustable counterweight is provided with a hydraulic control circuitand power cylinders which automatically adjust the counterweight toattain weight balance at any attitude of the loading arm when the arm iseither empty, partially full, or full.

Background of the invention The general field of art to which thepresent invention pertains is in marine loading arms for conveyingfluids to and from tank vessels, and more particularly concernscounterbalance, power-operated marine loading arms.

Marine loading arms for transferring liquid cargo to and from vesselsare now widely used, primarily because they are more efl'lcient and safethan flexible hoses, and can be installed in compact batteries ofmultiple loading arm units. Various systems for remotely positioningloading arms have been devised, one of which employs a movablecounterweight that balances the considerable weight of the extended armso that power cylinders of reasonable size can be used, and so that thepivotally interconnected conduits are for the most part self-supportingand require only minimum bracing. One difficulty with this type ofloading arm is that the balancing force is not constant to provide theoptimum counterbalancing action, because the conduits not only assumedifferent attitudes during positioning, but may be full, partially full,or empty. These conditions are obviously most acute in loading armsconstructed of large-diameter conduits having a large extended length.

Summary of the invention The inner conduit section of a marine loadingarm projects from a horizontal pivot axis and is provided with a leverarm extending in the opposite direction from the pivot axis. Movablealong the lever arm is a counterweight. Individual power means areprovided for pivoting the conduit section and for moving thecounterweight, the control system for the power means being so arrangedthat the moment of the conduit section, and its associated partsincluding the manifold coupling on the terminal conduit section andvarious swivel joint couplings, automatically adjusts the counterweightalong the lever arm to provide a proportional counteralance force. Bythis arrangement, a near optimum counterbalance is attained irrespectiveof the attitude of the loading arm or whether it is full, partiallyfull, or empty.

FIGURE 1 is a diagrammatic side elevation of the loading arm of thepresent invention.

FIGURE 2 is a diagrammatic rear elevation of the structure shown inFIGURE 1.

FIGURE 3 is an enlarged, diagrammatic elevation, partially broken away,of the general area indicated by the arrow 3 on FIGURE 2.

FIGURE 4A and 4B are schematic hydraulic control and power circuits forgoverning extension, retraction and the counterbalancing force of theloading arm.

FIGURE 4C is a schematic circuit similar to FIGURE 4B, but illustratinga different operational condition.

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Description of the preferred embodiment With reference to FIGURES 1 and2, the conventional features of the marine loading arm 10 include ariser assembly 12 which is mounted upon a dock or the like adjacent aberth or mooring location for a tank vessel. The riser assembly isprovided with a flanged inlet elbow 13 which by means of a pipeline (notshown) coupled thereto transfers fluid to or from the loading arm 10through a vertically disposed riser pipe 14.

A swivel pipe coupling 16 is mounted atop the riser pipe 14 and isconnected to a 90 degree pipe elbow 18. The elbow 18 supports the latermentioned components of the loading arm 10 for rotation about thevertical axis of the riser pipe 14. In order to prevent excessive loadsupon the swivel pipe coupling 16, a vertical strut 20 is connectedbetween a flange 22 (FIG. 3) on the elbow 18, and a lateral yoke 24(FIG. 2) which embraces a sleeve 26 on the riser pipe 14.

A swivel pipe coupling 28 (FIG. 3) and an elbow 29 interconnect theelbow 18 with an inner pipe section 30, thus mounting the pipe sectionfor pivotal movement about the horizontal axis of the coupling 28 in theusual manner. Similarly, a 90 degree elbow 32 (FIG. 2) on the outer endof the inner pipe section 30 carries a swivel pipe coupling at 34 whichby means of an elbow 36 is connected to an outer pipe section 38 andmounts the outer pipe section for movement relative to the pipe section30 about a second horizontal axis including the swivel pipe coupling at34.

The free end of the outer pipe section 38 is provided with a manifoldcoupling assembly 40 (FIG. 1) which includes a flange valve 42 that isbolted to the manifold of a tank vessel when the loading arm 10 istransferring fluid. The manifold coupling assembly 40 also includes ahorizontally disposed swivel pipe coupling 44 (FIG. 2)- and an adjacentsheave 46 that mount the coupling assembly 40 for remotely actuatedpowered movement about the turning axis of the swivel pipe coupling 44.Thus, the sheave 46 is secured to the coupling assembly 40 and one endof a cable 48 is secured to the sheave. The cable 48 is trained around afreely rotatable sheave 50 which is associated with the swivel pipecoupling at 34 (FIG. 2), and extends alongside the inner pipe section 30to and partially around a lower sheave 52 (FIG. 3). The lower sheave 52circumscribes thepivot axis of the pipe section 30 and is rotated withthe'pipe section when the pipe section is pivoted to pay out or pull inthe cable 48 and thus, in a known manner, automatically keep the boltingflange of the valve 42 upright.

Pivotal movement of the outer pipe section 38 relative to the inner pipesection 30 is also effected in a known manner. For this purpose, asheave 54 is anchored to the inner end portion of the outer pipe section38, and a sheave 56 (FIG. 3) is secured to the flange 22 adjacent thelower sheave 52. A cable 58 is trained around the sheaves 54 and 56, isanchored to the latter sheave, and includes a single-acting hydrauliccylinder 60 in each run of the cable intermediate the sheaves. By meansof a later described hydraulic control circuit, the cylinders 60 arealternately energized so that one cable run or the other is pulledtoward a cylinder 60 to swing the outer pipe section 38 relative to theinner pipe section 30.

Power means for pivoting the inner pipe section 30 is generallyconventional insofar as the power source and the driving method isconcerned, and includes a sprocket 62 (FIG. 3) which is non-rotatablerelative to the pipe section 30 and is bolted to the lower sheave 52.Achain 64 is wrapped around the sprocket 62, and each flight of thechain extends outward along the inner pipe section 30 toward a crossbar66 that is welded to the pipe section. Connected between the crossbar 66and each chain flight 64 is a single-acting hydraulic cylinder 68. Thecylinders 68, by means of the later described hydraulic control circuitshown in FIGURES 4B and 4C, are alternately energized in the manner ofthe cylinders 60 and thus in conventional manner rotate the inner pipesection 30 about the horizontal axis of the swivel pipe coupling 28(FIG. 3).

Further details which are known from prior art structures include adiagonal tension strut 70 (FIG. 2) between the crossbar 66 and thevertical strut 20, a similar strut 72 (FIG. 1) between the sheave 54 andthe outer pipe section 38, and other reinforcement means such as variousribs and flanges at 74 (FIGS. 1 and 2) which are welded together and tothe inner pipe section 30.

Extending rearward of the inner end portion of the inner pipe section30, and in general alignment therewith, is a rigid beam 78 whichslidably mounts a group of heavy cast plates comprising a counterweight80. As in similar marine loading arms, the counterweight 80 isadjustable along the beam 78, in the present instance by means of a pairof hydraulic cylinders 81 which are anchored to the beam 78 and havetheir piston rods coupled to the counterweight, so that the moment ofthe counterweight force times its lever arm (beam 78) approximates themoment of the loading arm times its effective lever arm. The effectivelever arm including the inner and outer pipe sections 30 and 38 variesaccording to the relative attitude of the pipe sections, and whether ornot the pipe sections are full, partially full, or empty. Althoughordinary marine loading arms may employ means for shifting acounterweight to balance the system throughout a range of operationalattitudes, the presence or absence of fluid in the loading arm willunbalance the arm according to whether or not the loading arm isdesigned to balance a full, empty, or partially empty arm assembly. Inother words, ordinary loading arms achieve optimum balance under onlyone of many different conditions resulting from the combination ofattitude and presence or absence of fluid in the arm. In the presentinvention, a near perfect balance is automatically achieved for all ofthe conditions noted, by means of the movable counterweight 80 (FIGS. 1and 2) and the specific hydraulic circuit shown in FIGURES 4B and 4C.

The hydraulic circuit of FIGURE 4A controls the power movement of theouter pipe section 38 through a manually operable hydraulic controlvalve 82 which, together with the other illustrated control components,may be removely located from the loading arm. The valve 82 is shown inan actuated position in which the parallel flow passages at 84 havedirected fluid into the left hand hydraulic cylinder 60 to lower theouter pipe section 38 from a raised position.

Valve 82 has a dead center 86 and crossed passages 88 which, whenrespectively aligned with a pressure line 90 and a return line 92 to areservoir 94, block the flow of fluid into the circuit from the mainsupply line 96, or reverse its flow direction to raise the outer pipesection 38. In the present instance, fluid under 1200 psi. has beentransmitted from the supply line 96 by the passages 84 to the left handcylinder 60 through a line 98, and through a conduit 100 from the righthand cylinder 60 back to the reservoir 94.

Raising of the outer pipe section 38 is accomplished by actuating thecontrol valve 82 to position the crossed passages 88 in place of thepassages 84, whereby fluid under pressure is transmitted through aneedle valve 102 which restricts the flow of fluid into (and from) theright hand cylinder 60. When the desired elevation of the outer pipesection 38 is attained, the control valve 82 is released and its deadcenter 86 is spring urged into flowblocking relation to the hydrauliclines 98 and 100.

Interconnecting the conduits 98 and 100 is a conduit 104 that iscontrolled by a solenoid operated, normally open valve 106. The solenoid108 of the valve 106 is automatically energized when the power unit, notshown, is turned on to supply the 1200 p.s.i. line pressure prior to theraising of the outer pipe section 38 as described. Accordingly, theelevational position of the raised outer pipe section is maintained aslong as the solenoid 108 is energized to close the valve 106, and aslong as the pressure in the lines 98 and does not exceed the 1250 psi.pressure setting of the usual pressure relief valves 110 which withassociated check valves 112 are connected between the lines 98 and 100.If such pressure setting should be exceeded, for example as might occurif the pipe section strikes an unyielding obstruction while being powerdriven, the lines 98 and 100 become interconnected through one of thecheck valves 110 and its associated check valve 112 so that the loadingarm will not be damaged.

With the outer pipe section 38 positioned in a desired location and thecoupling assembly 40 connected to the manifold of a vessel, the operatorof the loading arm turns off the power unit to deenergize the solenoid108, whereby the valve 106 returns to its normally open position and theouter pipe section 38 is free to move up or down with the vessel. At thesame time, of course, the inner pipe section 30 is similarly free tomove.

As thus far described, the structure of the loading arm 10 and thehydraulic circuit in FIGURE 4A are generally in accord with knownpractice in prior art loading arms.

With primary reference to FIGURES 4B and 4C, a LOWERING valve 114 and aRAISING valve 116 respectively control downward and upward movement ofthe inner pipe section 30. Each valve is manually operated. If thecounterweight 80 is in an unbalanced position, the actuation of eithercontrol valve to pivot the inner pipe section 30 will actuate thecounterweight cylinder 81 and cause a proportionate movement of thecounterweight 80 (FIGS. 1 and 2) along the beam 78 to achieve a nearoptimum counterbalancing action. Thus, the hydraulic circuit will adjustthe counterweight to correct imbalance caused by the presence or absenceof fluid in the loading arm before the loading arm is moved toward orfrom its rest position or its operative position.

As a direct result of this improved counterbalance arrangement, theloading arm pipe sections 30 and 38 can have a large capacity (a largediameter and length) and yet have the compactness and mobility formerlyattainable only with loading arms of smaller capacity.

Beginning with an assumed rest position (FIG. 4B) in which the innerpipe section 30 of the loading arm 10 is upright and the hydrauliccircuit has not been previously actuated, one possible position of thecounterweight 80 is in its maximum extended position away from the pivotaxis of the pipe section 30. Another possible position for thecounterweight is the maximum retracted positions shown in FIGURES 1 and2. When the power unit is energized to provide the control circuit withfluid under pressure, the actuating solenoid 117 of a normally openvalve 118 is energized to block flow communication between a line 120and a line 122 which are individually connected to the hydrauliccylinders 68 that control powered movement of the inner pipe section 30.

To initiate lowering movement of the pipe section 30, the control valve114 is actuated so that its straight passages at 124 respectivelytransmit fluid under pressure from the supply line 96 into a deliveryline 126, and complete a flow return path in a return line 128 to thereservoir 94. Part of the fluid in the delivery line 126 passes througha check valve 130 and a flow control valve 132, the latter valve havinga bypass check valve 134, into the line 120 which powers the left handor lowering cylinder 68 to lower the pipe section 30. However, becausethe counterweight 80 is in a maximum extended position, the availablepressure in the cylinder 68 is insuflicient to retract the piston rod ofsaid cylinder.

Consequently, the operating fluid (at 12 00 p.s.i.) is

diverted through an adjustable resistance valve 136, which is set toopen at a pressure in excess of 300 p.s.i., and is transmitted through aline 138 into the counterweight cylinders 81 in a direction causingretraction of their piston rods. The counterweight 80 is thus movedinward or toward the pivot axis of the inner pipe section 30. Only thenear cylinder 81 is shown in FIGURE 4B, and the other cylinder 81 isconnected in parallel with the cylinder which is illustrated.

After the counterweight 80 is moved sufficiently toward the pivot axisof the pipe section 30 to counterbalance the loading arm to the extentthat the pipe section 30 can be lowered withxa pressure of 300 p.s.i.exerted against the piston in the LOWERING cylinder 68, the valve 136closes and the line pressure is thus directed entirely to the LOWE-RINGcylinder 68. When the counterweight cylinder is moving thecounterweights, the fluid exhausted from behind the piston istransferred through a line 140, a check valve 142, a line 144, andanother check valve 146, a line 144,- and another check valve '146 intothe reservoir 94 via the return line 128 and one of the parallel valvepassages at 124 of the control valve 114. When the LOWERING cylinder 68is energized, the RAIS- ING cylinder 68 exhausts fluid to the reservoir94 through the conduit 122, a flow control valve 150 having a bypasscheck valve 152, and a line 154 which is connected to the line 144.

. Thus the setting of the resistance valve 136 causes the valve toresist just enough pressure (300 p.s.i.) for the LOWERING cylinder '68to lower the pipe section 30, when the loading arm is in a balancedcondition, due to the automatic positioning of the counterweight 80. Asthe pipe section 30 is lowered, its moment increases, but theelevational movement of the counterweight beam 78 causes the moment ofthe counterweight to likewise increase and the two moments are, andremain, substantially equal. It is believed evident from the precedingdescription that the control circuit provides means for sensing themoment differential between the loading arm and the counterweight 80,relative to the pivot axis of the pipe section 30, and also providesmeans for bringing the two moments into close balance.

While the pipe section 30 is being lowered, flow from the exhaustingRAISING cylinder 68 is resisted by the flow control valve 150 to cushionthe movement of the arm. When the appropriate lowered position isattained and the flanged valve 42 (FIG. 1) is maneuvered with theouterpipe section 38 until the valve can be coupled to the shipsmanifold, the actuator of the LOWERING valve 114 is released andhydraulic pressure in the main supply conduit 96 can be shut off. Thiscauses deenergization of the solenoid 117 whereby the valve 118 returnsto its normally open position to provide flowcommunication between thelines 120 and 122. Since the LOWERING valve 114 is now in its FIGURE 40off. position, line pressure to the system is blocked off. An openhydraulic circuit exists between the LOWERING and RAISING cylinders 68through the now open valve 118, and any drifting, rising or falling ofthe tank vessel which may cause the inner pipe section 30 to change itsattitude is thus to a large degree unopposed by the cylinders 68.

The valve 42 (FIG. 1) may then be opened to start a fluid transferoperation through the loading arm 10. If sudden vessel movement shouldpull the loading arm and cause movement of the pipe section 30suflicient to develop a pressure in excess of 1500 p.s.i. in eithercylinder 68, or if the loading arm when being maneuvered into couplingcondition strikes a moving obstacle causing the same condition, one oftwo pressure relief valves 160 will transmit the fluid through anassociated check valve 162 into one or the other of the lines 120 and122. At the end of a fluid transfer operation, the valve 42 is manuallyclosed preparatory to uncoupling the loading arm and retracting it toits rest position shown.

The loading arm in its presently described condition is full of fluidand is consequently unbalanced, because the counterweight is in aposition to balance the arm when empty. The power is turned on torestore line pressure in the main supply line 96, and the solenoid 117(FIG. 4C) is thus energized to close the valve 118. Because the valve118 and the LOWERING and RAISING control valves 114 and 116 are closed,there is no exhaust path for the fluid in the RAISING cylinder 68. Thepressure of this fluid when the valve 42 (FIG. 1) is uncoupled risesabove line pressure since the arm is unbalanced, but is less than the1500 p.s.i. setting of the relief valves 160. Consequently, even thoughthe arm is unbalanced, it remains in position while the valve 42 isuncoupled from the ships manifold.

The counterweight 80 must now be moved away from the pivot axis of thepipe section 30 to restore proper balance, and this is automaticallyeffected, in a manner similar to the previously described counterweightmovement, when the RAISING control valve 116 is actuated to the positionshown in FIGURE 4C. The parallel passages at 164 (FIG. 4C) are alignedwith a pressure line 166 and a return line 168 to transmit line pressureinto a line 170 for energizing the RAISING cylinder 68 and thecounterweight cylinders 81, and for opening an exhaust path for theLOWERING cylinder 68 to the reservoir 94 through a line 172.

The line pressure of 1200 p.s.i. is transmitted through a check valve174 and the line 122 into the RAISING cylinder 68, but due to theunbalanced condition of the loading arm the pressure is not sufiicientto retract the piston rod of the cylinder. Consequently, the fluid isdiverted through a resistance valve 176, which is set to open at 300p.s.i., and into the line 140 which is connected to the counterweightcylinder 81. After the counterweight 80 is moved outward along the beam78 to a position where the loading arm is so balanced that a pressure of300 p.s.i. will raise the arm by retracting the piston of the RAISINGcylinder 68, the valve 176 closes and all of the line pressure istransmitted to the RAISING cylinder 68.

In rising from its lowered position, the eflective moment of the loadingarm decreases, and the moment of the counterweight decreasesproportionately so that a near perfect balance is maintained until (andafter) the pipe section 30 reaches it FIGURE 1 rest position. Unless thefluid in the loading arm is drained, the loading arm is in balancedcondition for a subsequent lowering movement of the pipe section 30because the hydraulic circuit for the counterweight cylinders 81 isisolated by the closed LOWERING and RAISING control valves 114 and 116.However, if the loading arm is to remain in a rest position for anyappreciable time, it is desirable to open the RASING valve 116 to bleedfluid from the counterweight cylinders 81 to lower the counterweight8t). If the counterweight is lowered, the fluid in the loading armshould also be drained off so that the next operation of the loading armbegins under the same conditions outlined for the first describedoperation.

When the pipe section 30 is raised 'as last described, the LOWERINGcylinder 68 is exhausted through the line 120, the flow control valve132, a line 178 and a check valve 180 to the reservoir '94 via the lines172, 168 and one of the parallel flow passages at 164 in the RAISINGcontrol valve 116. Similarly, when the counterweight 80 is moved outwardto elfect the initial balance as described, the line 138 carries theexhaust fluid to a check valve 182 which communicates with a flowcontrol valve 184. Since the counterweight 80 might be moved downwardfor a balancing operation or for storing the arm when the pipe section30 is upright, gravity will assist such movement and the flow controlvalve 184 restricts the speed of downward movement of the counterweight.

It the loading arm is lowered, empty and unbalanced with thecounterweight fully extended a subsequent raising of the arm after ithas been uncoupled from the manifold of the vessel does not require anyrebalancing of the counterweight because it already overbalances theempty loading arm and thus tends to automatically return the loading armto its rest position even though the control circuit is not actuated.Under these conditions a fail-safe condition exists and the hydraulicsystem acts as a brake to damp the return movement of the loading arm byexhausting the LOWERING cylinder 68 through the flow control valve 132to reservoir.

The various pressures mentioned in the preceding description are, ofcourse, design considerations related to the physical size of thevarious components of the loading arm. It should be noted, for example,that the loading arm can be designed so that a pressure above or belowthe pressure settings of the resistance valves 136 and 176 will elfect apressure transfer from the counterweight cylinders 81 to the LOWERINGand RAISING cylinders 68 in order to sequentially sense the momentdifferential, balance the moments by adjusting the moment of thecounterweight, and then raise or lower the pipe section 30.

It will be apparent that the herein disclosed automatic balancingoperations do no require that the loading arm be either full or empty offluid, but that optimum balance is achieved for the loading arm in anypartially filled condition.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and varia tion may be made without departing from what isregarded to be subject matter of the invention as set forth in theappended claims.

Having completed a detailed description of the invention so that thoseskilled in the art could practice the same, I claim:

1. A marine loading arm comprising a rigid pipe section, means pivotallymounting said pipe section for movement about a substantially horizontalpivot axis, a counterweight carried by said pipe section and movabletoward and away from said pivot axis, first hydraulic power meanscoupled to said pipe section for regulating the elevational position ofthe free end of the pipe section, second hydraulic power means coupledto said counterweight for adjusting the position of said counterweightrelative to said pivot axis, and an hydraulic control circuit coupled tosaid first and second power means for automatically sensing the momentdifferential, as indicated by hydraulic fluid pressure, between saidpipe section and said counterweight relative to said pivot axis.

2. Apparatus according to claim 1 wherein said second power meansadjusts said counterweight relative to said pivot axis in proportion tosaidmomcnt differential and reduces said differential to a predeterminedvalue.

3. Apparatus according to claim 2 wherein said counterweight in adjustedposition produces a moment substantially equal to the moment of saidpipe section, and wherein said control circuit includes means forlocking said {counterweight in said adjusted position.

4. Apparatus according to claim 1 including a second rigid pipe section,means pivotally interconnecting said first and second pipe sections forfluid intercommunication and for relative pivotal movement about asubstantially horizontal axis, third power means coupled to said secondpipe section for effecting said relative pivotal movement, saidcounterweight in said adjusted position producing a moment substantiallyequal to the efifective moment of said first and second pipe sections.

5. Apparatus according to claim 1 wherein said first power meanscomprises a pair of hydraulically actuated cylinders, said controlcircuit including a conduit selectively pressurized with hydraulic fluidand connected to each cylinder for transmitting fluid under pressure toeflect the power stroke of the cylinder, said second power meansincluding a double-acting hydraulic cylinder connected to saidcounterweight, a bypass conduit connected to each of said selectivelypressurized conduits, said bypass conduits being connected to oppositeends of said double-acting cylinder, and a resistance valve arranged forone direction flow only in each bypass conduit, said resistance valveseach opening at a predetermined pressure existing in its associatedpressurized conduit to transmit said fluid into said double-actingcylinder and thereby adjust said counterweight.

6. Apparatus according to claim 5 in which said pipe section ispivotable about said axis when the pressure differential between one ofsaid presurized conduit-s in pressurized condition, and the assiciatedone of said bypass conduits in pressurized condition, approximates saidpredeterminined opening pressure for the associated one of saidresistance valves in order to effect a pressure transfer from saidbypass conduit to said pressurized conduit.

References Cited UNITED STATES PATENTS 1,344,659 6/1920 Sjoberg 212-491,497,686 6/ 1924 Johnson 212-49 2,368,268 1/ 1945 Spiegcl 212-493,073,343 1/1963 Mowell et a1. 137-615 3,221,771 12/ 1965 Dollinger137-615 HOUSTON S. BELL, J 11., Primary Examiner U.S. c1. X.R.

